Adhesively supported sanitary napkins

ABSTRACT

A sanitary napkin is provided with adhesive means which, while providing great in-use tenacity, is readily releaseable, both from the protective release strip and the undergarment. The adhesive means comprises an elongated band of pressure-sensitive adhesive extending longitudinally on the bottom surface of the napkin and disposed centrally thereon. The band of adhesive terminates in at least one peak.

United States Patent [191 Ginocchio Aug. 5, 1975 ADHESIVELY SUPPORTEDSANITARY NAPKINS [75] Inventor:

[73] Assignee: Personal Products Company,

Milltown, NJ.

[22] Filed: Feb. 15, 1974 [21] Appl. No.: 442,707

James A. Ginocchio, Summit, NJ.

[52] US. Cl. 128/290 R; 128/290 W [51] Int. Cl. A61f 13/16 [58] Field ofSearch... 128/290 R, 290 W; 156/291,

[56] References Cited UNITED STATES PATENTS 2,994,359 8/1961 Westbrooket al. 156/578 3,135,430 2/1964 Caldwell v. 156/578 3,463,690 8/1968Converse et a1. 156/291 Hawkins 156/433 3,665,923 5/1972 Champaigne, Jr.128/290 W 3,672,371 6/1972 Roeder 128/290 R 3,676,269 7/1972 Schaetti..156/283 3,682,738 8/1972 Smith 156/283 3,688,771 9/1972 Werner 128/290 R3,736,931 6/1973 Glassman.. 128/290 R 3,793,121 2/1974 Eberly, .lr.156/522 Primary ExaminerAldrich F. Medbery Attorney, Agent, or FirmJasonLipow [57] ABSTRACT A sanitary napkin is provided with adhesive meanswhich, while providing great in-use tenacity, is readily releaseable,both from the protective release strip and the undergarment. Theadhesive means comprises an elongated band of pressure-sensitiveadhesive extending longitudinally on the bottom surface of the napkinand disposed centrally thereon. The band of adhesive terminates in atleast one peak.

6 Claims, 8 Drawing Figures ADHESIVELY SUPPORTED SANITARY NAPKINSBACKGROUND OF THE INVENTION This invention relates to sanitary napkinsand more specifically to sanitary napkins employing adhesive means forsupporting the napkin when in use. The prior art is now replete withsuggestions for sanitary napkins comprising an absorbent'core encased ina soft liquid pervious cover and having, on one surface of the cover,pressure-sensitive adhesive means provided for attaching the napkin tothe crotch portion of an undergarment so as to support the napkin in useand maintain it in the proper in-use position. Generally, these napkinsare provided with a protective release strip overlying thepressure-sensitive adhesive and protecting it from dirt andunintentional adhesion when packaged, stored and handled, prior to use.At the time of use, the strip is peeled from the adhesive means and thenapkin is positioned and adhered to the undergarment. After use, thenapkin is peeled from the undergarment and disposed of.

The adhesive system employed in such products must meet several,sometimes conflicting, criteria. In use, it is important that the napkinadhere tenaciously to the undergarment at all times and so the adhesivesystem must resist moisture, the sudden torques exerted by movements ofthe body and the frictional shearing forces exerted by the movements ofthe various layers of clothing worn by the user. Notwithstanding theadherence tenacity required of the adhesive system during use, it isimportant that the protective release strip be easily peeled from theadhesive prior to use without tearing the napkin cover which, forreasons of economy, is generally a thin, soft, non-woven materialexhibiting little resistance to tearing. After use, it is essential thatthe napkin release from the undergarment without tearing the napkincover or the fabric of the undergarment.

Prior art adhesive systems generally represent a compromise betweenthese conflicting criteria. For example, a broad, generally rectangular,band of adhesive running longitudinally along the surface of the napkinprovides excellent in-use adhesive tenacity. Unfortunately, theforcesrequired to peel the protective release strip from such an adhesive bandare relatively large and account for a high incidence of napkin covertearing, particularly at the leading edge of the adhesive band.

An alternative system is disclosed in US. Pat. No. 3,672,371, issued onJune 27, l972,to Robert J. Roeder. As disclosed therein, the broadadhesive band is replaced by two parallel, narrow, spaced apart lines ofadhesive. Such a system provides excellent release characteristics withrespect to peeling the release strip from the napkin and peeling thenapkin from the un- I completely detached, even by a force appliedthereto dergarment. Unfortunately, adhesion in use has been for a shortduration, than a system having a single broad band where only a portionof the band will become detached over the same short duration. While itis true that body pressure will generally result in reattachment of thetwo-line napkin, the napkin is subject to being reattached out ofposition. On the other hand, a napkin having only a partially detachedbroad adhesive band will at all times remain in the proper position andhence, will reattach in the proper position.

For the above reasons, a completely satisfactory adhesive system hasnot, heretofore, been available.

SUMMARY OF THE INVENTION A sanitary napkin is now provided with adhesivemeans which, while providing great in-use tenacity, is also readilyreleasable, both from the protective release strip and the undergarment.The napkin may comprise the usual elongated absorbent core enclosed in afluid pervious wrapper. In accordance with this invention, adhesivemeans are provided on the bottom surface of the napkin (the side facingaway from the body in use) which comprise an elongate band ofpressure-sensitive adhesive extending longitudinally on said bottomsurface and disposed centrally thereon, the band of adhesive terminatingat at least one end thereof in at least one peak. It has been discoveredthat, provided that at least one end of the longitudinally extendingadhesive terminates in at least one peak, the adhesive band may be aswide or as long as is desirable or necessary in providing sufficientin-use tenacity and, in contrast to the prior art, there will be noconcomitant degradation in release characteristics such as tearing ofthe napkin cover.

When a napkin is provided in accordance with the teachings of thisinvention, a releasable protective strip may be provided to overlie theadhesive and when this strip is peeled from the peaked end of theadhesive band substantially less initial peeling force is required thanthe conventional blunt-ended adhesive systems. Accordingly, less stressis initially applied to the napkin cover precluding failure of thecover. Similarly, when the napkin is peeled from the undergarment afteruse, the initial peeling force applied is substantially less, insuringthat the napkin cover will not fail.

While it is not essential, it is desirable that the longitudinallyextending adhesive band terminate in at least one peak at each endthereof to provide the convenience of peeling from either end of thenapkin. It is also contemplated that the terminal end of the band havemore than one peak as the advantages which accure to this invention areequally applicable to multipeaked bands.

The invention may be advantageously applied to all adhesively attachedsanitary napkins. However, modifications in the napkins may be made totake specific advantage of the low initial peeling forces associatedwith the invention. For example, a thinner wrapper may be employed,i.e., one which is water dispersible for easy disposability in a watercloset and the fact that this wrapper is less resistant to tearing maybe overcome by employing the adhesive system of this invention. Asanother example, a pressure-sensitive adhesive having less adhesivetenacity per unit area may be employed since the constraint as to theadhesive band size has been relaxed by the methods of this invention,i.e., a greater area may be employed rather than a tackier adhesivewithout concomitantly degradating the release characteristics of thenapkin.

In another aspect, the invention also contemplates a method of applyinga flowable pressure-sensitive adhesive band to the bottom surface of thenapkin to obtain the peaked ends prescribed herein. The bottom surfaceis passed under an adhesive applicator having a wiping surface incontact with the bottom surface. The wiping surface of the applicator isprovided with an undercut portion, essentially the same width as that ofthe desired adhesive band. A feed hole is provided in this undercutportion and means are provided for intermittently supplying adhesivethrough the feed hole to the bottom surface of the napkin. The napkin ispassed under the applicator and adhesive flow is commenced. As theundercut begins to fill, and then is filled, with adhesive, the wipingaction of the bottom surface of the napkin against the wiping surface ofthe applicator produces an adhesive pattern of first increasing, andthen essentially uniform, width on the bottom surface, Le, a peak at theleading end of the adhesive band and then a portion of essentiallyuniform width. After the desired length of the essentially uniformportion has passed under the applicator, flow of adhesive is terminatedand the undercut portion begins to empty. The wiping action of thebottom surface which continues to move under and in contact with thewiping surface of the applicator results in a band of decreasing width,i.e., a peak at the trailing end of the adhesive band. In a similarmanner, an applicator may be provided with multiple feed holes toproduce multiple peaks at each end of the adhesive band.

BRIEF DESCRIPTION OF THE DRAWING Referring to the drawing:

FIG. 1 is a perspective view looking down on the bottom surface of asanitary napkin embodying the teachings of this invention and showingthe release strip partially peeled therefrom;

FIG. 2 is a sectional view of the napkin of FIG. 1 taken along line 22;

FIG. 3 is a perspective view ofa portion of a prior art napkinillustrating schematically the forces required for peeling off therelease strip;

FIG. 3a is a perspective view of a napkin embodying this invention andillustrating schematically the forces required for peeling off therelease strip;

FIG. 4a is a schematic, cross-section of a machine line for producingthe napkins of this invention;

FIG. 4b is a schematic cross-sectional plan view of the machine line ofFIG. 4a, for making a first embodiment of this invention;

FIG. 4c is a schematic cross-sectional plan view of the machine line ofFIG. 4a, for making a second embodiment of this invention; and

FIG. 4d is a schematic cross-sectional plan view of the machine line ofFIG. 4a, for making a third embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 and 2 illustrate anembodiment of the invention and specifically depict a sanitary napkin10, with its bottom surface 12 facing upward in the drawing. The napkincomprises an absorbent core 14 which may be made up of any suitableabsorbent material such as, for example, comminuted woodpulp fibers,cotton linters, rayon fibers, cotton staple, bleached sulfite crepedwadding and the like. The core 14 is surrounded by a fluid perviouscover 16 having longitudinal edges 18 and 20 overlapping and secured onthe bottom surface 12 of the napkin. The ends 22 and 24 of the cover 16extend beyond the core 14 and are sealed to hold the core fullyenclosed.

The cover may be of any of the commonly used covers such as gauze,non-woven materials reinforced with adhesive binders, or the newlydeveloped flushable non-woven fabrics designed to be readily dispersedin water and be easily disposed of by flushing away in a water closet.An example of this latter non-woven cover is provided in US. Pat. No.3,554,788 issued on Jan. 12, 1971 to M. R. Fechillas. A band ofpressuresensitive adhesive 26 is applied to the bottom surface of thenapkin and is located thereon to extend longitudinally and centrallythereto. Advantageously, the adhesive penetrates the cover of the napkinand aids in sealing the overlapped longitudinal edges 18 and 20 inplace. The adhesive band may comprise any of a large number ofpressure-sensitive adhesives available on the market, including, forexample, the so-called cold pressure-sensitive adhesives such as theacrylate adhesives, for example, vinyl acetate -2 ethyl hexyl acrylatecopolymer which is generally combined with tackifiers such as, forexample, ethylene amine. Alternatively, the adhesive may comprise therapid-setting thermoplastic (hot melt) adhesives such as blockcopolymers exemplified by styrene and butadiene styrene copolymers. Theadhesive band may also comprise a two-sides adhesive tape and theadvantages of this invention will accrue equally well to thisconfiguration. As will be more fully discussed hereinafter, there isparticular advantage in employing an adhesive which may be applied in aflowable state. However, the invention is not limited to any specificadhesive but applies as well to the use of non-flowable adhesive systemsalthough some inconvenience in production may thereby be incurred.

The adhesive band may be of any width or length sufficient to providesatisfactory adhesion, when the napkin is applied to an undergarment inuse. While the choice of band dimensions are, to an extent, governed bysuch factors as the particular adhesive used, and the nature of theundergarment to which it is being attached, generally the adhesiveshould be of a width of more than one-fourth-inch. The band may extendlongitudinally for a length corresponding to thefull length of the coreor even longer (extending onto the sealed ends of the cover), ifdesired. Generally, however, because of the unique features of thisinvention which allow a wider band to be used, it is unnecessary for theband to extend beyond the length of the core and, in fact, the band maybe substantially less than this length.

The band is protected by a releasable strip 32, illustrated in FIG. 1 ina partially peeled off position, and provided to protect the adhesiveduring storage and handling prior to use. In accordance with theteachings of this invention, the adhesive band terminates in at leastone peak, two such peaks, 28 and 30, being shown in FIG. 1.

While it is sufficient that only one end of the band terminates in atleast one peak, it is advantageous that both ends be provided with sucha peaked pattern so as to facilitate peeling from either end.

The advantage of the peaked adhesive configuration are best illustratedin FIGS. 3 and 3a. In FIG. 3, a broad blunt-ended adhesive band 34, suchas is found in some prior art products, is illustrated with thereleasable strip 36 being initially peeled. The wide blunt end of theadhesive band 34 requires a substantial force, shown schematically bythe arrow labeled F in the drawing, to be applied to the releasablestrip 36 in order to initiate peeling. It is believed that, while thisforce tends to be fairly well-distributed at the adhesive edge/coverinterface, because the napkin cover tends to lift away from the core andcrease or pucker when the peeling force is applied to the strip, theforces designated as F in the drawing, transmitted to a point forward ofthe interface, are again consolidated and approach a substantial portionof the total force F applied to the strip. This substantial consolidatedforce F, acting on a point on the napkin cover, is believed to be thecause of napkin tearing. In contrast thereto, FIG. 3a illustrates aportion of a napkin having a peaked adhesive band 38 in accordance withthe teachings of this invention. l-Iere, because of the unique peakeddesign of the terminal end of the adhesive band 38, a substantiallylower initial peeling force, designated by the arrow labeled fin thedrawing, is required to be applied to the release strip 40. Accordingly,the forces transmitted to the napkin cover are concomitantly less, shownas f in the drawing, and preclude napkin cover tearing. Of course, oncethe releasable strip 40 has been peeled beyond the peaked portion of theadhesive pattern, the forces which must be applied are the same as thoseapplied to the prior art product. This does not create a problem,however, because these forces are then resisted by the portion of thecover which has the adhesive band applied thereto and so the adhesiveacts as reinforcement for the cover at this point in the peelingprocess, again precluding cover tearing. It will be understood by oneskilled in the art that the foregoing analysis applies equally well tothe removal of the napkin from the undergarment after use.

In view of this analysis, it becomes apparent then that the forcesexerted on the napkin cover in the prior art configuration are, to alarge measure, a function of the width of the adhesive band. Said inother words, the width of the adhesive band applied to the napkin inaccordance with prior methods is limited by the resistance of the napkincover to tearing. In contrast thereto, the adhesive pattern of thisinstant inventionis essentially unlimited by the napkin tearingresistance and so may be as wide as is necessary and desirable inproviding satisfactory in-use adhesion.

Numerous variations in the design of conventional adhesively attachednapkins will become apparent in view of the teachings of this invention.For example, a less tear resistant napkin cover may now be employed, andparticularly, a napkin cover which is more readily dispersible in awater closet and hence, more easily disposed of. Also, a less teneciousadhesive may be employed, as the total adhesive strength of a givenadhesive may be increased by increasing the width of the adhesive band.Further still, a shorter band may be employed by increasing the width.Other variations will occur to those skilled in the art in view of theteachings herein.

Referring now to FIG. 4a, illustrated therein, is a method for producingthe product of this invention and specifically depicted, in schematicalvertical cross section, is a machine line for applying the adhesivepatterns prescribed herein. FIGS. 4b-d depict a horizontalcross-sectional view of the same machine line as shown in FIG. 4a andfurther illustrate several embodiments of the present invention.

As shown in these figures, an assembly comprising napkin cores 44,wrapped in a non-woven cover 46 but not yet cut into individual napkins,is moving from right to left in the drawings, past an adhesiveapplicator 48. The assembly may be moved by an endlessly rotating beltor by another carrier means. It is also possible that the adhesiveapplicator may move and the assembly remain stationary.

The applicator 48 comprises a bottom wiping surface 50 which is inwiping contact with the surface of the moving assembly on which theadhesive pattern is to be applied. The wiping surface of the applicatoris provided with an undercut portion 52, of a width essentiallycorresponding to the desired width of the uniform portion of theadhesive band. A feed hole is provided for delivering adhesive to thewiping surface 50, through the undercut 52. Means, not shown in thedrawing, are provided for intermittently delivering adhesive through thefeed hole. Such means may comprise a gravity or pressure feed adhesivesystem flowing through a feed control valve which is opened and closedby an electrically timed switch, the timing of which is coordinated withthe relative speed of the web, with respect to the wiping surface of theapplicator, to deliver adhesive in the proper sequence. Alternatively,the adhesive may be forced to flow through the feed hole by the actionof a pump which is likewise activated by a timed electrical controlsystem. Many other variations for sequentially delivering a flowablematerial to a moving assembly may be employed as the adhesive deliverymeans. 7

In accordance with this invention, the flow of adhesive is begun at thepoint in time when the napkin assembly is positioned under theapplicator so that the desired position for the leading end of they peakof the adhesive pattern is directly under the feed hole. As adhesivefeed is continued, the adhesive tends to spread in a directioncorresponding to the width of the undercut, and gradually fills theundercut. A pattern is then wiped onto the surface of the napkinassembly which has an increasing width until a point in time is reachedwhen the flow of adhesive has completely filled the undercut.Thereafter, the pattern wiped onto the surface of the assembly is of anessentially uniform width. A point in time is reached when the assemblyhas traveled a sufficient distance past the applicator so that theposition on the surface of the assembly where it is desired to begin toapply a peak to the lagging edge of the adhesive band is directly underthe undercut portion. The feed to the undercut portion is thenterminated and the undercut begins to empty, wiping an adhesive patternonto the assembly surface which has a decreasing width, thus forming theterminal peak. The sequence of starting and stopping the flow ofadhesive is then repeated as the next portion of the assembly passes theapplicator.

As can be best seen by an inspection of FIG. 4b-d, the width of theadhesive band can be controlled by properly selecting the width of theundercut 52. The length of the band can be controlled by selecting theproper timing sequence. The number of peaks at each end of the adhesiveband is directly related to the number of feed holes provided in theapplicator, i.e., in FIG. 4b, one feed hole produces a single peak ateach end;

in FIG. 4c, two holes produce two peaks; and in FIG. 4d, three holesproduce three peaks.

As aforesaid, the novel napkin having a peaked adhe sive band greatlyreduces the initial peeling force required to remove the releasableprotective strip from the napkin without a concomitant loss of in-useadhesion. The following example illustrates this advantage.

EXAMPLE Samples are prepared by applying an adhesive band to anelongated l-inch wide strip of non-woven material as described in theaforementioned U.S. Pat. No. 3,554,788 issued to M. R. Fechillas. Theadhesive is an acrylate copolymer of vinyl acetate and 2-ethyl hexylacrylate. Three samples are provided with an elongated band of adhesive,three-eights inches wide, centrally located on the strip, and having ablunt leading edge as illustrated in FIG. 3 of the drawing. A secondthree samples are provided with an elongated band of adhesive, againthree-eighths inch wide and centrally loeated but, however, having theends of the adhesive band terminating in three peaks as are illustratedin FIG. 4d of the drawings. The distance between the ends of the peaksand the uniform portion of the adhesive band in these peaked samples isabout three-fourths inch. Each sample is placed on a clean stainlesssteel plate, adhesive face down and adhered to the plate by moving a lb.roller weight across the sample at a rate of 12 inches per minute. Thesamples are then peeled from the plate at an angle of 180C. by grippingthe leading edge of the fabric in the jaws of an lnstron testeroperating at a peeling rate of 6 inches per minute. The lnstron testeris equipped with a recorder-plotter which plots the force-distancefunction of each peel test. The peeling is carried out on each samplefor a peeled distance of three-fourths inch, corresponding to the peaklength of the peaked samples. The forcedistance function of each peeltest is integrated by use of a planimeter to obtain the work required topeel each of the samples the initial three-fourths inch. The results arereported in the Table below.

Peaked Sample in.-lbs.

Blunt Sample (in.-lhs,) Difference 4.23 3.17 25 3.37 3.06 9 3.29 1.9939.4 Average: 3.63 2.74 24.4

What is claimed is: 1. In an elongate sanitary napkin provided withpressure-sensitive adhesive disposed on the bottom surface thereof forattaching said napkin to a supporting garment, the improvement whereinthere is provided means for insuring ready releasability of the napkinand garment, said means comprising providing said pressure-sensitiveadhesive in'the form of a single band extending longitudinally of saidbottom surface and being centrally disposed thereon with respect to thelongitudinal sides thereof, said band of adhesive terminating at atleast one end thereof in at least one peak.

2. The napkin of claim 1 wherein said adhesive band terminates at eachend in at least one peak.

3. The napkin of claim 1 wherein said band of adhesive terminates at atleast one end in a plurality of peaks.

4. The napkin of claim 3 wherein said band terminates at each end in aplurality of said peaks.

5. The napkin of claim 1 wherein said band is more than one-fourth inchwide.

6. A method of applying the adhesive band of claim 1 comprising:

passing the bottom surface under an adhesive applicator, said applicatorhaving a wiping surface in contact with said bottom surface, an undercutportion in said wiping surface with at least one feed hole in saidundercut portion and means for intermittently supplying adhesive throughsaid feed hole to said bottom surface; starting the flow of adhesivethrough said feed hole to form an adhesive pattern on said bottomsurface of increasing and then essentially uniform width as saidadhesive, respectively, begins to fill, then fully fills the undercutportion; and I stopping the flow of adhesive to form an adhesive patternof decreasing width as said undercut portion is emptied;

whereby at least one peak is formed at each end of the adhesive band.

1. In an elongate sanitary napkin provided with pressuresensitiveadhesive disposed on the bottom surface thereof for attaching saidnapkin to a supporting garment, the improvement wherein there isprovided means for insuring ready releasability of the napkin andgarment, said means comprising providing said pressure-sensitiveadhesive in the form of a single band extending longitudinally of saidbottom surface and being centrally disposed thereon with respect to thelongitudinal sides thereof, said band of adhesive terminating at atleast one end thereof in at least one peak.
 2. The napkin of claim 1wherein said adhesive band terminates at each end in at least one peak.3. The napkin of claim 1 wherein said band of adhesive terminates at atleast one end in a plurality of peaks.
 4. The napkin of claim 3 whereinsaid band terminates at each end in a plurality of said peaks.
 5. Thenapkin of claim 1 wherein said band is more than one-fourth inch wide.6. A method of applying the adhesive band of claim 1 comprising: passingthe bottom surface under an adhesive applicator, said applicator havinga wiping surface in contact with said bottom surface, an undercutportion in said wiping surface with at least one feed hole in saidundercut portion and means for intermittently supplying adhesive throughsaid feed hole to said bottom surface; starting the flow of adhesivethrough said feed hole to form an adhesive pattern on said bottomsurface of increasing and then essentially uniform width as saidadhesive, respectively, begins to fill, then fully fills the undercutportion; and stopping the flow of adhesive to form an adhesive patternof decreasing width as said undercut portion is emptied; whereby atleast one peak is formed at each end of the adhesive band.